1. Field of the Invention
The present invention relates to a semiconductor chip having a gettering layer for removing impurities such as heavy metals, and to a method for manufacturing the same.
2. Background Art
In the manufacture of semiconductor devices, heavy-metal contamination due to copper and nickel, and the like leads to the destruction of gate insulation films or the deterioration of element reliability, and is one of causes to lower the yield of devices. The heavy-metal contamination occurs not only in the process for forming an element layer including transistors or the like on the surface of a wafer (first-half process), but also in the process for dicing the wafer and assembling the semiconductor chips into a package (second-half process).
In order to prevent heavy-metal contamination, it is effective that a gettering layer for removing (gettering) heavy metals is previously formed in the part of a wafer or a semiconductor chip (for example, refer to Japanese Patent Laid-Open No. 2001-250957, or Japanese Patent Laid-Open No. 56-56660).
When a package having a structure wherein a plurality of semiconductor chips are laminated, such as a multi-chip package (MCP), is used, the thickness of each semiconductor chip must be thinned in the second-half process in order to raise the integration degree of the device.
By doing this, since the gettering layer formed inside or on the back face of the wafer in the first-half process is lost or thinned, there have been problems wherein the element layer is contaminated by heavy metals in the second-half process, and the yield of devices are lowered due to the defect of the gate insulation film.